There are 4 books in the Mermaids to the Rescue series.
The Mermaids to the Rescue series does not have a new book coming out soon. The latest book, Cascadia Saves the Day (Book 4), was published in March 2019.
The first book in the Mermaids to the Rescue series, Nixie Makes Waves, was published in March 2019.
The Mermaids to the Rescue series primarily falls into the Fantasy genre.